There are many encryption schemes available to computer users for secure file transfer, but most require that the user download a software application for encryption of the file before sending the file. Tumbleweed, in U.S. Pat. No. 5,790,790 to Smith et al., developed a less burdensome document delivery system that is used by many delivery companies to facilitate delivery of “e-packages,” but the scheme suffers from drawbacks. One of the most significant drawbacks is the system's use of relatively weak encryption based on the Secure Sockets Layer, which cannot be changed without a fundamental alteration of the transfer scheme.